Caption: DNA strand. Coloured transmission electron micrograph (TEM) of a single strand of DNA (deoxyribonucleic acid). DNA usually exists as a condensed, super-coiled form in the chromosomes, which are found in the nucleus of every cell. The chromosomes uncoil during cell division, allowing the DNA to make an identical copy of itself. DNA consists of nucleotide bases attached to a sugar- phosphate backbone. The sequence of the four bases (adenine, guanine, cytosine and thymine) in DNA directs the assembly of amino acids to form proteins. In this way, DNA provides the necessary information to create a new organism.